Three traveling salesmen, short on money, decide to share a room in a really cheap flea-bag hotel.
The desk clerk tells them the room is $30, payable in advance, so they each give him a $10 bill and retire for the night.
Then the desk clerk realizes that he overcharged the salesmen; the room should have been $25. He gives the bellhop five singles, with instructions to give the money to the salesmen.
The bellhop is a bit dishonest, however, and tells the salesmen that they are due a refund of $3. He gives $1 to each salesman, and keeps the other $2 for himself.
So each salesman has paid a net amount of $9, or $27 for all three. The bellhop has $2.
Question: what happened to the other dollar of the original $30?